Self là đối tượng

import pygame

pygame.init()
screen = pygame.display.set_mode((640, 480))
pygame.display.set_caption("Falling Star")
clock = pygame.time.Clock()

class Star:
    def __init__(self, x, y):
        self.x = x
        self.y = y
        self.speed = 2

    def update(self):
        self.y += self.speed
        if self.y > 480:
            self.y = 0

    def draw(self, screen):
        pygame.draw.circle(screen, (255, 255, 255), (self.x, self.y), 4)


star = Star(320, 0)

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    star.update()

    screen.fill((20, 22, 40))
    star.draw(screen)
    pygame.display.flip()
    clock.tick(60)

pygame.quit()